Jimmy Westlake

Two thousand years ago, St. Matthew recorded in his gospel that something extraordinary appeared in the sky over Bethlehem of Judea that heralded the birth of Jesus. For centuries, astronomers have wondered about the nature of this Star of Bethlehem. Was it a one-time supernatural event, never seen before and never seen since? While that is a possibility, it seems unlikely that St. Matthew would have been the only person in the world to record the appearance of an amazing event like that.

Another possibility is that the Star of Bethlehem was a rare but natural celestial event that might have gone unnoticed by the masses but would have drawn the attention of sky watchers, such as the wise men mentioned in St. Matthew's gospel. Assuming this to be the case, what type of object might it have been?

A bright comet would have been witnessed and recorded by sky watchers all over the world, but no record of such a comet at that time exists, so this explanation seems unlikely.

The spectacular death of a nearby star as a supernova explosion would have made a spectacular and temporary star in the heavens, but supernovas leave telltale signs like expanding clouds of gas that modern astronomers would have found had there been one. No such supernova remnant has been found from that time period.

The best natural explanation for the Star of Bethlehem is that an unusual grouping of the bright planets in the sky might have been interpreted by sky watchers of the day as a sign heralding the birth of a king. Running the solar system clock backward, astronomers have identified two very unusual groupings of the planets that might have been the Star of Bethlehem. One occurred in 7 B.C., and the other in 2 B.C. Both of these planetary groupings involved Jupiter, considered to be the king of the planets.

On the morning of June 17, in the year 2 B.C., the two brightest planets visible in our sky, Jupiter and Venus, appeared to pass so close to one another that they would have blended into a single bright object for a few brief hours. Could this have been the heavenly sign that launched the Magi on their journey westward to Judea, where they found the young child Jesus? Unless other ancient records are found that give us more and better clues, this is as good a guess as any that astronomers can make.

This Christmas season, Venus is visible in the southwestern sky just after sunset, and Jupiter is visible in the eastern sky just before sunrise. The two planets are not nearly as close together as they appeared in 2 B.C., but it is still interesting to gaze at them today and wonder at the possibilities.